In the process for manufacturing semiconductor devices, pressure sensitive adhesive sheets have been heretofore employed, and in general, on a pressure sensitive adhesive layer of such a pressure sensitive adhesive sheet, a release liner having on a substrate a release layer made of a release agent composition containing a silicone compound is laminated to protect the pressure sensitive adhesive layer.
The silicone compound, however, generally has properties such that it is liable to migrate and therefore, it is thought that if such a pressure sensitive adhesive sheet is used in the field of semiconductors, the silicone compound that constitutes the release layer migrates into the pressure sensitive adhesive layer to cause troubles of circuits of the semiconductor devices. Because of this shortcoming, a release liner having a release layer made of a release agent containing no silicone compound has been desired.
As the release agent containing no silicon compound, an alkyd resin type release agent, an olefin resin type release agent, an acrylic resin type release agent having a long-chain alkyl group (also referred to as a “long-chain alkyl type release agent” hereinafter) or the like has been proposed.
The alkyd resin type release agent, however, presents a problem in that its uses are restricted because of high peel strength. The olefin resin type release agent has a problem in that a pressure sensitive adhesive layer cannot be formed on the release liner because of poor heat resistance. The long-chain alkyl type release agent presents a problem in that a pressure sensitive adhesive agent cannot be applied to the release liner because of poor solvent resistance and has a problem of poor adhesion to a substrate such as a film.
Under such circumstances as mentioned above, a release agent composition wherein an ultraviolet-curing functional group was introduced into the long-chain alkyl type resin has been proposed in order to solve the above problems of the long-chain alkyl type release agent (see, for example, Japanese Patent Laid-Open Publication No. 183619/2003). In the use of such a release agent composition, however, there occurs a problem that the apparatus for manufacturing semiconductor devices needs a measuring device or a dryer for curing ultraviolet rays.
Further, a release agent composition wherein a functional group, such as a hydroxyl group, a carboxyl group or an epoxy group, was introduced into the long-chain alkyl type resin has been proposed (see, for example, Japanese Patent Laid-Open Publication No. 147327/2003 and Japanese Patent Laid-Open Publication No. 290610/2000). However, if a functional group is introduced into the long-chain alkyl type resin that is a major agent to form a crosslinked structure, degree of freedom of the long-chain alkyl group is decreased, and therefore, surface energy of the release layer is hardly lowered, that is, there occurs a problem that control of release force becomes difficult.
It is an object of the present invention to provide a long-chain alkyl group containing acrylic resin type release agent composition which exhibits excellent solvent resistance, heat resistance and adhesion to substrate without exerting evil influence on electronic parts and the like and which is capable of controlling peel strength, and a release liner having a release layer made of the composition.